Fire alarm signalling system

ABSTRACT

Air samples are removed through ducts connected to the spaces to be supervised on the one hand, and to a distribution valve on the other, which selectively switches the ducts through to a pump, which applies the sample from a selected space, through dust, water vapor, and carbon dioxide removing filters, as well as through other filters, to a carbon monixide (CO) detector which, upon detection, gives an alarm signal and further preferably controls the pump and the control valve to pump out more sample air from the particular space in which an increased CO content was detected. The CO detector may be an infrared (IR) spectroscope, a gas chromatograph, a system catalytically oxidizing CO to CO2, and then detecting CO2, a hot-wire detector, chemical detectors, of a fuel cell, or the like.

United States Patent 1191 Purt FIRE ALARM SIGNALLING SYSTEM [541 3,420,636 I 1/1969 Robbins 23/232 R x 3,545,929 12/1970 Linnenbom et a1. 23/232 E [75] Invent F' RaPPeSwL 3,553,461 1/1971 Siano et a1. 340/23'/ R Switzerland OTHER PUBLICATION [73] Assignee: Cerberus AG, Mannedorf, S

Switzerland M1nch1n et 81., Chemistry & Industry, Mar. 6, 1948, p.

147-149. [221 Flledi July 1971 Katz et 31., Can. J. Res. 26, 318-330 1948) [21] App]. No.: 164,738

Primary ExaminerR0bert M. Reese 301 Foreign Application Priority Data Flynn 1 31,1970 S l d 11607 .111 y witzer an /70 [5,7] ABSTRACT [52] US. Cl. 23/232 R, 23/254 R, 340/237 R Air samples are removedthrough ducts connected to [51] Int. Cl. G0ln 31/00, G08b 21/00 the spaces to be supervised on the one hand, and to a [58] Field of Search 23/232, 232 E, 254 E, distribution valve on the other, which selectively 23/254 R; 340/237 R, 237 S; 136/86 B, 86 R, switches the ducts through to a pump, which applies 153; 204/195 R, 195 S the sample from a selected space, through dust, water vapor, and carbon dioxide removing filters, as well as [56] References Cited through other filters, to a carbon monixide (CO) de- UNITED STATES PATENTS tector which, upon detection, gives an alarm signal 1,891,429 12/1932 Ljunggren 23/232 R and further preferably Commls the l" and the 1 908 202 5/1933 White 23/232 E valve to Pump more sample mm the 2:384:463 9/1945 Gun 8L t l 136/86 R ticular space in which an increased CO content was 2,443,427 6/1948 Kidder et al. 23/232 X detected- The C0 detector y be an infrared 2,813,010 11/1957 Hutchins 23/232 R spectroscope, a gas chromatograph, a system catalyti- 2,833,629 5/1958 Carbonara et a1. 23/254 E cally oxidizing CO to CO and then detecting CO a 3,027,552 3/1962 Landis 23/232 R X hot wire detegtor, chemical detectors, of a fuel cell, or 3,028,490 4/1962 011111611X 340/237 R the mm 3,209,343 9/1965 Dunham et a1. 340/237 R 3,284,165 11/1966 Baumann et a1. 340/237 R X 30 Claims, 9 Drawing Figures Superwkory Indicator m 14 I per zfctor i l m fl/arm 179w ll Hydrocarbon: u i 21:51] +54 Filter S Control Dust Hater, Vapor, C0 l7 Pulse 7 IJ'ourre a 1B 15 Contra/led I Valves l 1 1 1 lamp/111g in 16 Duals PATENIEDHBI 16 ms 3; 765L842 SHEET 3 BF 3 47 Reaczor L9 and Sens/n flnalyzer ircuit X Preheazer 46 Heat l.a

\ 1.5 Oxidazion Cartrid 2:: $2

Thermocouples f f R L" //50 ea: C0 Filter .2 Detector CHIlT/dge 2 Fig-5 T Fig. 5

Reference 57 se 56 Cell Ce 71' Heated f 1 59 Platinum 58 Wire 52 EEK Signs/n 51 60 Circu/ 55 I F|g.7

Fig. 8 66 Fuel C8 63 65 64 Fig. 9

1 FIRE ALARM SIGNALLING SYSTEM The present invention relates to a fire alarm signalling system and more particularly to such a system in which air samples are removed from spaces to be detected and applied to a detection or sensing element which, when a certain characteristic is exceeded, gives an alarm signal. The present invention utilizes the presence of carbon monoxide as a detection characteristic.

Fire alarm systems have been proposed in which various characteristics and phenomena incident to a fire are utilized to give an alarm when a fire has been sensed. As an example, temperature sensitive elements or temperature sensitive switches and thermostats can be used to sense increase in temperature. It has also been proposed to indicate the presence of a fire by sensing radiation of light, in the visible, ultraviolet, or infrared range by suitable UV and IR detectors. Such temperature or flame detectors have the disadvantage that they will respond only when a fire has spread to such an extent that either there is a measurable temperature increase or that flames are already present. If such apparatus is made highly sensitive, it is subject to false alarms and to give spurious responses, since temperature increases, or radiation in the sensitive range can be caused by other sources than by a fire.

The beginning of a fire should be indicated as soon as possible; it is therefore desirable to utilize those characteristics and phenomena which are present as soon as a fire starts. Early warning detection systems of this type may utilize optical smoke detectors which indicate the presence of a fire as soon as smoke is sensed. Ionization type fire alarm systems are particularly suitable since the smoke aerosolsare present already at the initial stage of a fire, and can be sensed, and thus utilized to give an alarm signal. Unfortunately, such apparatus is also subject to spurious responses, and thus to give false alarms. Smoke and aerosol indicators can be caused to respond by dust particles. Other systems for fire alarm have been proposed, but all of them can be triggered to false alarms by spurious phenomena.

It has also been proposed to increase the sensitivity of fire alarm systems by taking air samples from the space to be supervised, and to conduct these air samples, by suction, over suction ducts to a measuring chamber. In comparison with fire alarm systems in which the air is conducted to the detection chambers merely by thermal convection, it has been found that mechanical suction systems have the advantage of higher sensitivity. Since, however, smoke, water vapor and dust will precipitate within the ducts, the length of the ducts must be held to a certain maximum and is limited due to rapid decrease in sensitivity as the duct length increases. Over periods of time, during which air is sucked through the ducts, the actual sensitivity of the system to fire may deviate substantially from the design sensitivity. Additionally, maintenance costs are substantial due to the frequent requirements for cleaning and testing, of the fire alarm system, as well as of the suction system.

It is an object of the present invention to provide an early warning fire alarm system which is capable of rapidly indicating the presence of a fire, which is reliable and not subject to spurious responses, which is sensitive and which retains its design sensitivity over an appreciable period of time, without substantial maintenance costs, and which requires only a limited number of sensors, and a small investment in detection equipment.

Subject Matterof the Present Invention Briefly, air samples are removed from the spaces and conducted to a detection chamber, in which a carbon monoxide (CO) sensitive detection element is located. Filters are provided to remove non-gaseous components before the samples are applied to the detection chamber.

The present invention is based on the fact that, as soon as a fire starts, solid and liquid products arise, such as smoke and aerosols; and, in addition thereto, gases evolve. Since practically all combustible substances in an unintentional fire always contain carbon, and, since in the initial stage of a fire combustion is incomplete, carbon monoxide is always present in the initial stages. In the initial stages of a fire there is usually insufficient heat for complete combustion. Carbon monoxide is a certain criterion for a fire, in contrast to other combustion products such as water vapor and carbon dioxide, so that a spurious response, and response to conditions not caused by a fire are a minimum. An additional advantage of testing for CO is, that CO is somewhat lighter than air and that CO will therefore rise to the ceiling of a space to be supervised, even without thermal convection due to the fire, so that suction openings for the detectors can be located in the ceiling and will respond even before sufficient heat has been generated by the fire itself to cause thermal convection. Other combustion products will be transported to the detection units only after the fire itself has caused sufficient heat.

CO has a rather similar molecular diameter as the molecules of the air. It is, therefore, possible to remove larger molecules and even the larger molecules of vapor-formed decomposition products by vary fine filters before the air is passed to the detectors or through the suction system. Presence of such filters does not change the mixture ratio with the air,-and thus the sensitivity, even if long ducts are used. The system is therefore particularly useful in environments subject to dust, such as in connection with suction systems, ventilation of silos, and the like. CO does not separate out. Since CO behaves practically similarly to air, only a small suction effort is required to transport CO, without decrease in sensitivity of the sensing element.

CO is, chemically, quite inert. It is therefore possible to remove gaseous components from the air sample by chemical reaction, before applying the air sample to the sensing element, without interfering with the sensitivity of the sensor to CO itself. Thus, hydrogen sulfide can be removed by contact with silver, or carbon dioxide by aqueous solutions of barium hydroxide, or the like.

Utilizing CO to detect fires has the additional advantage that a rapid indication of the presence of CO is given. CO is extremely poisonous, so that warnings should be given in any case as soon as the CO content of the air exceeds the danger limit which is at approximately ppm, that is, 100 10 percent.

Any known CO detector may be used with the fire alarm system in accordance with the present invention, for example apparatus for catalytic combustion, or chemical reaction of CO with a suitable reaction substance, and test for the reaction product; or apparatus testing for the physical characteristics of CO, such as optical measuring instruments, gas chromatographs, molecular spectrographs, or the like. The type of apparatus selected will depend on requirements; in general, those apparatus which have high sensitivity as well as long life with low maintenance costs and which are particularly selective to C are eminently suitable.

The invention will be described by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a general schematic diagram of the fire alarm signalling system with a CO detector;

FIG. 2 is a schematic diagram of a filtering system;

FIG. 3 is a schematic transverse sectional view of an IR absorption CO detector;

FIG. 4 is a schematic diagram of a gas chromatographic CO detector;

FIG. 5 is a schematic diagram of a CO detector with catalytic oxidation and sensing of heating;

FIG. 6 is a schematic diagram of a CO detector with oxidation and CO indication;

FIG. 7 is a CO detector utilizing a palladium chloride reaction;

FIG. 8 is a schematic diagram of a CO detector with adsorption of platinum; and

FIG. 9 is a CO detector utilizing a fuel cell.

General principle, with reference to FIG. 1: Two spaces 1, 2 to be supervised are formed in the ceiling with openings 3 which may include mechanical coarse filters. Each one of the ceiling openings is connected to a sampling duct 4 which connects to a bank of control valves 5. The valve system of the bank of valves 5 is controlled by an electrical circuit to be discussed below so that in accordance with a certain timed program the various sampling ducts 4 from the openings 3 are opened through the valvesto form communication with a common duct 6 leading to a pump 7. In accordance with another embodiment, which is useful for certain applications, all lines are constantly placed on suction and the particular line to be sampled is switched by the controlled valve to a bypath leading to the detection unit. This substantially decreases the response time of the alarm system.

The output of pump 7 is applied to the apparatus to sense the presence of carbon monoxide (CO). This apparatus includes a selective filter system 8, 9 and a detector unit 10, through which the air samples are passed by the pump 7. Any suitable, and for example known CO sensing apparatus can be utilized in the detector l0, utilizing specific physical, chemical, electrical, or optical characteristics of carbon monoxide, or a reaction thereof, and supplying an electrical output signal when the level of carbon monoxide being sampled exceeds a predetermined level. Especially suitable C0 detectors will be described below in connection with the further figures. Some of those detectors, however, are sensitive not only for CO but also respond to other gases or substances which may be contained within the ambient air in the spaces 1, 2, or could be damaged thereby. Depending on the type of CO detector utilized, it is therefore desirable to interpose one or more filters in the ducts leading to the detector. These filters, additionally, can be used to separate nongaseous components of the air being supplied, for example dust or vapors. The arrangement of the filters can be chosen as necessary, for example, immediately adjacent the inlet openings 3, in the separate sampling ducts 4, in advance of pump 7, or behind the pump 7 and immediately in front of the detection unit. Me-

chanical filters are preferably applied directly in front of the inlet openings 3 since, a pump which selectively can apply suction and air pressure can then, by reversal of the air path, be used for self-cleaning of the entire system. The pump 7 and the valves are then suitably controlled by a synchronized timing program, applying, as' desired, suction, or a reverse air stream. If necessary, several filters, having similar or different functions can be interposed at various points of the system.

The arrangement in accordance with FIG. 1, which is merely illustrative, shows that between pump 7 and CO detector 10, a first filter 8 is placed which absorbs dust, water vapor and carbon dioxide; thereafter, a selective filter 9 is placed which absorbs S0 H 8 and hydrocarbons. These filters are preferably matched to the detector unit to be used, so that the entire system comprising filter and detector is selective to carbon monoxide.

Detector 10 is 'so arranged that when a predetermined amount of CO in the air sample applied thereto is exceeded, an electrical alarm signal is applied to an alarm circuit 11. If desired, a certain time delay may be built into the system, to eliminate short-time spurious responses.

Alarm circuit 11 applies a signal to an alarm control unit 12, which is connected to one or more supervisory indicators 14 over line 13, to indicate audibly or visually the presence of an alarm condition. Additionally, a line 15 is connected to alarm units 16 located within the space from which the air is derived and which caused the alarm system to respond, that is, in which a fire has been sensed, so that theindividual alarm unit 16 will immediately indicate the presence of a tire in the space being supervised.

Alarm circuit 11 additionally is connected to a line 17 which connects to a pulse source 18 which is connected over lines 19 and 20 to pump 7, and the valve unit 5, respectively. The pulse source 18 is so arranged that, in normal, non-alarm condition, the various valves 5 which are preferably magnetically operated are opened in a predetermined sequence, to connect (or bleed) sampling ducts 4 sequentially to the common line 6 leading, eventually, to the CO detector. Thus, the CO detector is supplied with air from the various openings 3. This avoids application to the detector of a mixture of atmosphere derived from the various spaces to be supervised which would cause decrease in concen- I tration of CO derived from a possible fire and thus application of a lower percentage of CO to detector 10. By sequential, regular scanning of all suction points, the CO detector can be cheaper since its sensitivity can be less. In those instances in which only one or only very few spaces are to be supervised, the valve distribution system and the associated electrical valve switching system may be omitted.

When the alarm circuit 11 has a signal applied thereto from C0 detector 10, pulse source 18 and pump 7 are controlled, by lines 19, 20, respectively, to an alarm condition. Pump 7 is preferably switched to a higher speed, that is to higher pumping effort, to provide increased suction and thus increased sampled air to the CO detector. The magnetic valve array 5 is so controlled that the particular valve, which was open when the excessive CO was sensed, is controlled to remain open, or at least to remain open for a longer period of time than the adjacent valves, or than normal. This increases further the reliability of the entire system and, by indicating which one of the valves had the increased CO concentration passing therethrough, provides an indication of the location of the initial alarm. The alarm itself is checked since the CO detector will continue to respond, and will respond stronger if a fire actually occurred, and the source of the fire is localized. Any suitable circuit can be used for further alarm indications or alarm transmissions, and the system can be coupled to an automatic sprinkler, or other fire extinguishing system.

FIG. 2 illustrates a filter system in schematic form. The filter separates and absorbs most of the interfering and damaging contamination occurring in air which is applied to a CO detector. Various elements of the system can be located along the path of air applied from inlets 3 to the CO detector, as desired. The filter system includes a mechanical dust filter 21, separating out solid and liquid particles. A mesh width of from 1 to p.is particularly advantageous. Next is a silica gel filter 22, to absorb water and water vapor. Filter 23 is a soda lime filter for the absorption of CO A further silica gel filter 24 absorbs various hydrocarbons, which is followed by a filter 25 containing activated charcoal to absorb H 8, 80:, and other gases. The last filter 26 is a selective filter for the absorption of additional interfering components, for example a silver contact filter, a cooling trap, or the like.

The various filters can be constructed with interchangeable filter cartridges, thus substantially facilitating maintenance. Not all the filters illustrated may be necessary under all conditions, and some'of them can be omitted if, for example, the specific CO detector which has been selected does not react with the respective substances being filtered out, or is not damaged thereby. The pump, further, can be placed at any suitable location, which may be different from that shown in the drawing. The sequence of the filters is best selected by matching the overall filter characteristics to the CO detector which is being used, and then suitably locating the filters in the path of the air being applied thereto. It is preferred to first place a dust filter 21 in the installations, since absorption of solid and liquid particles before the air enters the system substantially decreases contamination and dirt within the entire system and thus substantially decreases maintenance costs.

Various CO detectors will be described in'connection with the other figures.

Embodiment of FIG. 3: An infrared (IR) detector utilizes the absorption of radiation within certain IR bands by CO molecules. A measuring chamber 27 has the air to be tested applied thereto from an inlet to an outlet. The measuring chamber 27 is subject to IR radiation, emitted from a source 28 of known construction. Radiation, which may be attenuated by the CO content of the air within chamber 27 is recorded in a photoelectric detector 29. A parallel path for IR radiation, and forming a reference path is located next to chamber 27, and includes a chamber 30 filled with cleaned air, an IR radiation source 31 (which may be combined with source 28 and suitably applied to chamber 30), and a photo element 32 which, again, can be combined with photo element 29 or can be the same element, operating on a time sharing basis. A rotating shutter 33 islocated in the path of the IR radiation through the two chambers 27, 30, selectively and sequentially applying radiation to be detected by the photoelectric pick-up. If the absorption of IR radiation in both chambers 27 and 30 is the same, then the photo detectors 29, 32 (or the single photo detector, in timed sequence) provide the same output voltage or current. If, however, absorption in the measuring chamber 27 increases due to presence of CO, the photo detectors will have a net output signal, in the form of square wave pulses, which can be applied to a sensing or utilization circuit 34, to be connected to give an alrm output signal. Utilization circuit 34 can be a simple a-c amplifier, which can be made selective to the frequency of interruption as determined by the speed of the rotating blade 33. A bridge circuit is also suitable; the circuit can also be made selective only to change in d-c level, with the outputs from detected radiation in chambers 27, 30, being conducted to the circuit 34 with reversed polarity so that, when they are in balance, they will cancel. Various other circuits and common in measuring technology can be used.

To make the apparatus particularly selective to respond to CO, a filter 35 can be located in the path of the IR radiation which passes only those frequency spectra of IR radiation in which CO has absorption bands. Such a filter 35 can be a conventional filter, for example may consist ofvapor deposited M4 layers. Filters of this type can be constructed so that they have a spectral path region which is very restricted, for example passing only a single spectral line, thereby effectively eliminating erroneous indications and interference by other gases.

Embodiment of FIG. 4: A gas chromatographic CO detector, in which air to be tested is taken in certain time intervals, for example every 20 seconds, automatically from the supply ducts and applied to a mixing and quantitizing device 36, in which the carrier gas applied from a supply 37, such as helium, hydrogen, or argon is mixed thereto. The mixture is applied to a known gas chromatographic separating column 38 which may, for example, contain a filling in the type of a molecular sieve. The gas, separated into components, is then applied to an analyzer 39 which may be a flame ionization detector, a catharometer or other analyzing apparatus of suitable type. The automatic mixing and quantitizing device 36, as well as the'analyzer 39 are controlled by means of a controller 40 so that an alarm is given only when CO is detected. A catalytic converter 41 is interposed before the input of the gas chromatographic apparatus which changes the carbon monoxide to methane in accordance with the following relation:

C0 3H, 2 CH H 0 Nickel is a suitable catalyst. The analyzer, of course, must be sensitive to CH, rather than CO.

Embodiment of FIG. 5: The catalytic oxidation of CO to CO in accordance with the relationship:

2 co o 2 co,+ 6 7.9 cal.

can be utilized. A suitable catalyst is I-Iopcalite (A mixture of the oxides of manganese and copper). The presence of CO is sensed by sensing the heat of reaction. The air, derived from the filter system is applied to detector 42, which first includes a pre-heater 43 and then the reaction cartridge 44 containing the catalyst. Two thermocouples 45, 46 of a thermal sensing system are FIG. 5, within the detector 42. An increase in temperature at the thermocouple 46 with respect to thermocouple 45 then is an indication that a reaction has taken place and that CO was present. To prevent outside influences from interfering and providing spurious signals, it is desirable to temperature-stabilize the entire detector 42. The thermal currents from the thermocouples are then sensed in a utilization circuit 47 which may, for example, contain a bridge circuit.

Embodiment of FIG. 6: Rather than determining the heat of reaction when CO is converted to C0,, the end product itself, that is, the CO itself can be detected. Any known method can be used, for example colorimetric or nephelometric analysis, or titration. Air to be tested is applied over a CO, filter 50 into a heated oxidation cartridge 48 which contains an oxidation substance as a catalyst, for example Ag MnO l-lopcalite, HgO, or 1 The actual reactor and analyzer 49 is then utilized for the determination of CO in accordance with any known method. One system, for example, uses the absorption in a Ba (OH solution with automatic back titration by means of oxalic acid by means of an indicator, with automatic change of samples. Precipitated BaCO can be indicated by nephelometric analysis by means of a filter, a spectral photometer or the like.

CO can also be absorbed in a slightly alkaline Ba (C109 solution and detected by coulometric analysis. The reaction Ba (C CO H 0 3 ZHCIO, Ba C0 Pd C1 C0 H O Pd CO HCl The precipitated palladium salt can be indicated by absorption measuring. The sample gas is applied. to a reaction vessel 51 which is located in the radiation path of a source 52, a filter 54, and a photo cell 53. Change in the photo current sensed by photo cell 53 is recorded in the sensing circuit 55. Of course, rather than a directly reading instrument, an instrument utilizing a reference cell, with a bridge-type measuring circuit or the like can be used.

Similarly, the reaction 1 0 5C0 5CO can be utilized and iodine (1 which is formed can be indicated, for example in a KI and starch solution. It is also possible to determine the presence of iodine by titration with sodium thiosulfate.

Other chemical reactions can be utilized, for example, the reaction C0 I-IgO Hg CO,

can be used for CO determination, for example by photometric determination of the degree of blackening of selenium sulfide by means of mercury vapor resulting due to the reaction Ultraviolet-spectroscopic determination of mercury vapor within a gas retort is also suitable.

Silver salt of sodium sulfamidobenzo acid with CO can be used in accordance with the relationship:

The silver salt which results is then photometrically determined in order to detect CO.

Embodiment of FIG. 8: A cell 56 has the sample air passed therethrough. A reference cell 57 is provided, in which clean air is located. Both cells have a platinum wire 58, 59 located therein which is heated to be red hot, connected in a bridge circuit by means of resistances 60, 61. As the resistance of the platinum wire 58 changes with respect to that of platinum wire 59, the cross connection of the bridge which includes a measuring instrument 62 will provide an indication, and thus can be utilized to provide an output signal.

Electrolytic determination of CO by selective adsorption on solid surfaces, at room temperature, or at increased temperature can also be utilized. Nickel is a suitable material. Electrical characteristics, which change upon adsorption, can then be utilized to provide an electrical output signal.

The various CO detectors, in which the CO content increases in the detector requires change in the detector elements, for example by interchanging cartridges, or a regeneration from time to time. The particular time lapse, as well as the type of regeneration will depend essentiallyon the amount of sample gas which passes through the test cartridge. Regeneration or exchange of test material cartridges can be suitably automated.

Embodiment of FIG. 9: A fuel cell forming measuring chamber 66 has the sample gas applied thereto. The CO containing sample gas is oxodized on an anode 63 which is covered with a selectively effective catalyst. A suitable electrolyte 65 is located between electrodes 63 and 64 of the fuel cell and, when CO is present, current will be supplied from the cell 66.

Modifications and preferred embodiments of the general system: If only a single space is to be supervised, then the various ducts 4 (FIG. 1) can be eliminated and the system can be made as a compact single unit. In a preferred form, at least one filter or filter system and a CO detector is, however, needed, as well as some kind of a suction providing arrangement, for example a small fan or ventilator. If a number of spaces are to be supervised, and filters are suitably located, for example at the inputs to the openings 3, then a single CO detection device (which forms the expensive part of the system) is all that is needed, with suitable switchover by valves 5.

The fire alarm system as described can be combined with presently available apparatus, for example airconditioning or ventilating systems. A separate suction or air circulation system can then be avoided and existing lines need only be tapped. Thermal circulation of air is frequently sufficient in order to supply a suitable quantity of gas to the indicator, since the lightness of CO, coupled with thermal circulation will provide a suitable stream of combustion gases, so that, in some installations, a positive suction apparatus need not be used. The alarm and indicating system can be combined with an automatically operating fire alarm central since an indication will be obtained not only that a fire is present, but, by sensing which ones of the valves supplied gases to the analyzer, an indication of the location of the fire is likewise obtained.

Various changes and modifications may be made within the inventive concept.

I claim:

1. Fire alarm system for a plurality of spaces to be supervised for the presence of fire comprising a detection chamber a plurality of duct means (3, 4, 5, 6, 7) for removing air samples from each said spaces and separately conducting said air samples to the detection chamber (10);

a controlled switchable valve (5) having a plurality of inputs, each input being connected to a duct, the output from the valve being connected to the detection chamber;

valve switching control means (18) connected to the valve and controlling switching of the valve, in steps, to sequentially connect one of the ducts through the valve to sample air drawn through the several ducts from the several spaces and connect the sampled air from any one duct to be directed to the detection chamber (10);

a pump (7) pumping air from said spaces through said ducts, and valve, to supply air to the detection chamber;

filter means (8) removing non-gaseous components from the air being applied to the detection chamber; I

means in said detection chamber responsive to the presence of carbon monoxide (CO) in said sample and providing an electrical alarm signal upon sensing the presence of CO above a predetermined level;

the alarm signal being connected to control increase of the quantity of air supplied from the respective duct connected through the valve (5) to the detection chamber (10) upon sensing of a CO presence in excess of said predetermined level.

2. System according to claim 1, wherein the alarm signal from the CO responsive means is connected to said switching control means (18) to control said coresponsible means to maintain a passage through the valve in communication with the detection chamber for a longer than normal period if the CO responsive means has sensed a CO presence in excess of said predetermined level.

3. System according to claim 1, wherein the alarm signal from the CO responsive means is connected to the pump and controls said pump for a higher pumping effort if said CO responsive means has sensed a CO presence in excess of said predetermined level.

4. System according to claim 1, wherein the pump is continuously operating to apply suction to said ducts and connected to apply air, as switched by said valve, to the detection chamber.

5. System according to claim 1, including alarm means (12, 13, 14, 15, 16) connected and responsive to said electrical alarm signal when presence of CO is sensed in excess of said predetermined level, said alarm means indicating from which one of the ducts connected to the switchable valve air was obtained causing said detection of excess CO level.

6. System according to claim 1, wherein said means removing non-gaseous components includes a mechanical filter system having a pass width less than about 10 Mmicrons).

7. System according to claim 1, wherein the filter means (8) is equipped to remove water vapor.

8. System according to claim 1, wherein the filter means is equipped to also remove C0 9. System according to claim 1, wherein the filter means is equipped to also remove S0 H 3, and hydrocarbons.

10. System according to claim 1, wherein said CO responsive means comprises means (37) providing a carrier gas; a mixer element (36) mixing air samples from said space with said carrier gas;

and a gas chromatographic column (38);

an analyzer (39);

and a controller (40), the controller being connected to control the mixer (36) and the gas chromatograph to provide an output signal only if the analyzer (39) records a carbon monoxide component in the air passing through the gas chromatographic column.

11. System according to claim 1, wherein the CO responsive means comprises means catalytically converting' CO with hydrogen to methane;

and means indicating the presence of methane.

12. System according to claim 1, wherein the CO responsive means comprises means including palladium chloride and water for reaction with CO; and means indicating the presence of palladium.

13. System according to claim 1, wherein the CO responsive means comprises means including iodine pentoxide and means reacting CO with iodine pentoxide and indicating the presence of iodine.

14. System according to claim 1, wherein the CO responsive means comprises means including mercury oxide and reacting CO with the mercury oxide, and means indicating the presence of mercury.

15. System according to claim 1, wherein the CO responsive means comprises means including a silver salt solution and means reacting the silver salt solution with with the detection chamber for a longer than normal period if the CO responsive means has sensed a CO presence in excess of predetermined level, and said alarm signal is additionally connected to the pump (7) to control said pump for higher pumping effort if said C responsive means has sensed a CO presence in excess of said predetermined level.

19. System according to claim 1, wherein the CO responsive means comprises a sensing chamber through which air from said spaces is passed;

and an lR spectroscope responsive to CO in said chamber.

20. System according to claim 19, wherein said IR spectroscope comprises a second chamber having non-contaminated air placed therein and forming a reference chamber; means alternately applying lR radiation to said reference chamber and to the sensing chamber;

and means sensing the difference in IR radiation passing through said chambers and providing said electrical alarm signal when the difference exceeds a predetermined level.

21. System according to claim 1, wherein the CO responsive means comprises means including a metallic surface, and means sensing the electrical properties of the metallic surface.

22. System according to claim 21, wherein themetallic surface comprises a heated platinum wire; and the means sensing the electrical properties comprises means determining the resistance change upon the presence of CO in the heated platinum wire.

23. System according to claim 1, wherein the CO responsive means comprises means for catalytic oxidation of carbon monoxide to carbon dioxide.

24. System according to claim 23, including means to sense heat liberated upon catalytic oxidation. 7

25. System according to claim 23, includingmeans sensing carbon dioxide formed upon catalytic oxidation.

26. Method of sensing the presence of a fire in a plurality of spaces comprising 7 removing atmosphere samples from the spaces to be supervised for the presence of fire;

selectively, sequentially switching atmosphere samples removed from various ones of said spaces; removing by filtering at least non-gaseous components from the atmosphere samples so removed; testing the filtered atmosphere for carbon monoxide content; and controlling the removing step to apply a greater amount of sampled atmosphere from a space in which an excess CO content has been determined, than from other spaces.

27. Method according to claim 26, wherein said filtering step comprises filtering with respect to at least one of: mechanical with a mesh width of about 10 p. or less; absorption of water vapor; absorption of carbon dioxide; absorption of sulphur dioxide, hydrogen sulfide, or hydrocarbons.

28. Method according to claim 26, wherein the testing step comprises at least one of infrared spectroscopy; gas chromatographic analysis in a gas chromatographic column; selective adsorption of a metallic surface, and determination of the electrical characteristics of the surface; direct conversion to electrical energy in a fuel cell.

29. Method according to claim 26, wherein the testing step comprises the step of reacting CO with another, predetermined substance and testing for the physical, or chemical characteristics of the reaction or the reaction product, said testing step comprising at least one of: reacting CO by catalytic reaction to CO and testing for reaction heat; reacting CO by catalytic reaction to CO and testing for CO reacting CO with hydrogen and testing for methane; reacting CO with palladium chloride and water, and testing for palladium; reacting CO with iodine pentoxide, and testing for iodine; reacting CO with mercury oxide and testing for mercury; reacting CO with a silver salt solution and testing for precipitated silver.

30. Method according to claim 26, wherein the testing step comprises modifying a substance by the CO content of the atmosphere and detecting the modified substance;

and further including the step of providing said substance in cartridge form, and periodically replacing said cartridge. 

2. System according to claim 1, wherein the alarm signal from the CO responsive means is connected to said switching control means (18) to control said co-responsible means to maintain a passage through the valve in communication with the detection chamber for a longer than normal period if the CO responsive means has sensed a CO presence in excess of said predetermined level.
 3. System according to claim 1, wherein the alarm signal from the CO responsive means is connected to the pump and controls said pump for a higher pumping effort if said CO responsive means has sensed a CO presence in excess of said predetermined level.
 4. System according to claim 1, wherein the pump is continuously operating to apply suction to said ducts and connected to apply air, as switched by said valve, to the detection chamber.
 5. System according to claim 1, including alarm means (12, 13, 14, 15, 16) connected and responsive to said electrical alarm signal when presence of CO is sensed in excess of said predetermined level, said alarm means indicating from which one of the ducts connected to the switchable valve air was obtained causing said detection of excess CO level.
 6. System according to claim 1, wherein said means removing non-gaseous components includes a mechanical filter system having a pass width less than about 10 lambda (microns).
 7. System according to claim 1, wherein the filter means (8) is equipped to remove water vapor.
 8. System according to claim 1, wherein the filter means is equipped to also remove CO2.
 9. System according to claim 1, wherein the filter means is equipped to also remove SO2, H2S, and hydrocarbons.
 10. System according to claim 1, wherein said CO responsive means comprises means (37) providing a carrier gas; a mixer element (36) mixing air samples from said space with said carrier gas; and a gas chromatographic column (38); an analyzer (39); and a controller (40), the controller being connected to control the mixer (36) and the gas chromatograph to provide an output signal only if the analyzer (39) records a carbon monoxide component in the air passing through the gas chromatographic column.
 11. System according to claim 1, wherein the CO responsive means comprises means catalytically converting CO with hydrogen to methane; and means indicating the presence of methane.
 12. System according to claim 1, wherein the CO responsive means comprises means including palladium chloride and water for reaction with CO; and means indicating the presence of palladium.
 13. System according to claim 1, wherein the CO responsive means comprises means including iodine pentoxide and means reacting CO with iodine pentoxide and indicating the presence of iodine.
 14. System according to claim 1, wherein the CO responsive means comprises means including mercury oxide and reacting CO with the mercury oxide, and means indicating the presence of mercury.
 15. System according to claim 1, wherein the CO responsive means comprises means including a silver salt solution and means reacting the silver salt solution with carbon monoxide to determine precipitated silver.
 16. System according to claim 1, wherein the CO responsive means comprises a fuel cell having CO applied thereto, the delivery of current by the fuel cell being an indication of the presence of CO.
 17. System according to claim 1, wherein the means in said detection chamber responsive to the presence of carbon monoxide include replaceable cartridges.
 18. System according to claim 1, wherein the alarm signal from the CO responsive means is connected to said switching control means to control said means to maintain a passage through the valve in communication with the detection chamber for a longer than normal period if the CO responsive means has sensed a CO presence in excess of said predetermined level, and said alarm signal is additionally connected to the pump (7) to control said pump for higher pumping effort if said CO responsive means has sensed a CO presence in excess of said predeteRmined level.
 19. System according to claim 1, wherein the CO responsive means comprises a sensing chamber through which air from said spaces is passed; and an IR spectroscope responsive to CO in said chamber.
 20. System according to claim 19, wherein said IR spectroscope comprises a second chamber having non-contaminated air placed therein and forming a reference chamber; means alternately applying IR radiation to said reference chamber and to the sensing chamber; and means sensing the difference in IR radiation passing through said chambers and providing said electrical alarm signal when the difference exceeds a predetermined level.
 21. System according to claim 1, wherein the CO responsive means comprises means including a metallic surface, and means sensing the electrical properties of the metallic surface.
 22. System according to claim 21, wherein the metallic surface comprises a heated platinum wire; and the means sensing the electrical properties comprises means determining the resistance change upon the presence of CO in the heated platinum wire.
 23. System according to claim 1, wherein the CO responsive means comprises means for catalytic oxidation of carbon monoxide to carbon dioxide.
 24. System according to claim 23, including means to sense heat liberated upon catalytic oxidation.
 25. System according to claim 23, including means sensing carbon dioxide formed upon catalytic oxidation.
 26. Method of sensing the presence of a fire in a plurality of spaces comprising removing atmosphere samples from the spaces to be supervised for the presence of fire; selectively, sequentially switching atmosphere samples removed from various ones of said spaces; removing by filtering at least non-gaseous components from the atmosphere samples so removed; testing the filtered atmosphere for carbon monoxide content; and controlling the removing step to apply a greater amount of sampled atmosphere from a space in which an excess CO content has been determined, than from other spaces.
 27. Method according to claim 26, wherein said filtering step comprises filtering with respect to at least one of: mechanical with a mesh width of about 10 Mu or less; absorption of water vapor; absorption of carbon dioxide; absorption of sulphur dioxide, hydrogen sulfide, or hydrocarbons.
 28. Method according to claim 26, wherein the testing step comprises at least one of infrared spectroscopy; gas chromatographic analysis in a gas chromatographic column; selective adsorption of a metallic surface, and determination of the electrical characteristics of the surface; direct conversion to electrical energy in a fuel cell.
 29. Method according to claim 26, wherein the testing step comprises the step of reacting CO with another, predetermined substance and testing for the physical, or chemical characteristics of the reaction or the reaction product, said testing step comprising at least one of: reacting CO by catalytic reaction to CO2 and testing for reaction heat; reacting CO by catalytic reaction to CO2 and testing for CO2; reacting CO with hydrogen and testing for methane; reacting CO with palladium chloride and water, and testing for palladium; reacting CO with iodine pentoxide, and testing for iodine; reacting CO with mercury oxide and testing for mercury; reacting CO with a silver salt solution and testing for precipitated silver.
 30. Method according to claim 26, wherein the testing step comprises modifying a substance by the CO content of the atmosphere and detecting the modified substance; and further including the step of providing said substance in cartridge form, and periodically replacing said cartridge. 